An integrated circuit includes a plurality of cells. A cell, such as a standard cell, includes one or more logic gates, e.g., a NOT gate or an inverter. In the design of the integrated circuit, the cells are retrieved from a cell library and are placed at locations in a layout. The cell library associates the cells with timing characteristics. During the design, simulation is performed on the layout verifying that the integrated circuit functions as intended. Simulation results can be made accurate by providing the cell library with realistic timing characteristics.